Polymer petroleum-based

In 2002, the world production of polymers (not including synthetic libers and rubbers) was ca. 190 million metric tons. Of these, the combined production of poly(ethylene terephthalate), low- and high-density polyethyelene, polypropylene, poly(vinyl chloride), polystyrene, and polyurethane was 152.3 milhon metric tons [1]. These synthetic, petroleum-based polymers are used, inter alia, as engineering plastics, for packing, in the construction-, car-, truck- and food-industry. They are chemically very stable, and can be processed by injection molding, and by extrusion from the melt in a variety of forms. These attractive features, however, are associated with two main problems ... 

In order to decrease human consumption of petroleum, chemists have investigated methods for producing polymers from renewable resources such as biomass. Nature Works polylactic acid (PLA) is a polymer of naturally occurring lactic acid (LA), and LA can be produced from the fermentation of corn. The goal is to eventually manufacture this polymer from waste biomass. Another advantage of PLA is that, unlike most synthetic polymers which litter the landscape and pack landfills, it is biodegradable. PLA can also be easily recycled by conversion back into LA. It can replace many petroleum-based polymers in products such as carpets, bags, cups, and textile fibers. 

Biobased polymers from renewable materials have received increased attention recently. Lactate is a building block for bio-based polymers. In the United States, production of lactic acid is greater than 50,000 metric tons/yr and projected to increase exponentially to replace petroleum-based polymers. Domestic lactate is currently manufactured from corn starch using the filamentous fungus Rhizopus oryzae and selected species of lactic acid bacteria. The produced lactic acid can then be polymerized into polylactic acid (PLA) which has many applications (Hatti-Kaul et al., 2007). However, so far, no facility is built to use biomass derived sugars for lactic acid production. More research needs to be done to develop microbes using biomass derived sugars for lactate production. 

PLA biodegradable polymer prices have fallen sharply over the last five years since the polymers were first commercialised. NatureWorks PLA is now available at prices between 1.37-2.75 per kg compared to a price range of 3.0-3.5 per kg five years ago. Another factor that is encouraging uptake is the stability of maize prices versus petroleum-based polymers. NatureWorks PLA has been price competitive with PET for example over the last twelve months as PLA manufacturing scale has increased and process improvements were made alongside the recent sustained higher levels of PET pricing. 

Rising prices for safflower and increasingly better water-based paints formulated from petroleum-based polymers rather than vegetable oils quickly cut industrial consumption of safflower oil. PVO attempted to stem this tide by introducing products that combined safflower oil with water emulsion technologies, but it was too late (49-51). 

Potential new uses for soy protein are driven primarily by environmental concerns and the search for new value-added uses for agricultural commodities. In addition, prices for petroleum-based polymers have increased relative to prices for... 

Another area is the production of chemical intermediates from renewable feedstocks. Cargill-Dow and Dupont are just two of the companies beginning to market biobased polymers and plastics to replace petroleum based polymers. Again, the fermentation fundamentals originally developed for food manufacturing continue to apply to a wide variety of products. 

Extrusion is a cost effective manufacturing process. Extrusion is popularly used in large scale production of food, plastics and composite materials. Most widely used thermoplastics are processed by extrusion method. Many biopolymers and their composite materials with petroleum-based polymers can also be extruded. These include pectin/starch/poly(vinyl alcohol) (Fishman et al. 2004), poly(lactic acid)/sugar beet pulp (Liu et al. 2005c), and starch/poly(hydroxyl ester ether) (Otey et al. 1980), etc. In this study, composite films of pectin, soybean flour protein and an edible synthetic hydrocolloid, poly(ethylene oxide), were extruded using a twin-screw extruder, palletized and then processed into films by compression molding process or blown film extrusion. The films were analyzed for mechanical and structural properties, as well as antimicrobial activity. 

The over growing environmental pressure caused by the wide spread consumption of petroleum based polymers and plastics has hastened the development of biodegradable and environmentally acceptable materials. Biopolymers derived from various natural resources such as proteins, cellulosics, starch and other polysaccharides are regarded as the alternate materials. Biodegradable polymeric materials derived from renewable sources are the most promising materials because of their easy availability and cost effectiveness. Biodegradable modified polysaccharides have been found to possess varied applications such as salt resistant absorption of water [109]. 

Biodegradable biopolymers (BDP) are an alternative to petroleum-based polymers (traditional plastics). It will be important to find durable plastic substitutes, especially in short-term packaging and disposable applications. The continuously growing public concern concerning this problem has stimulated research interest in biodegradable polymers as alternatives to conventional non-degradable polymers such as polyethylene and polystyrene, etc. The economic value of renewable raw materials will increase to a significant extent [1] and induce new industrial activities [2,3]. 

The cell as a biosynthesis machine can use cheap carbon sources (waste products) as precursor substrates to produce bacterial polymers. However, the in vitro synthesis of biopolymers requires costly purified key enzymes and precursor molecules such as ATP, coal, coal bolsters, and nucleotide sugars or sugar acids to synthesize polymers such as PHA, cellulose, alginate, and PGA. Consequently, these polymers have limited commercial applicability due to their very high production costs. It is estimated the production of PHB by in vitro synthesis would amount to a cost of around US 286,000 per gram of PHB whereas, bacterial production of PHB was estimated to cost about 0.0025 per gram of PHB, and this is still 5-10 times as expensive to produce as the respective petroleum-based polymers. 

Figure 6.1. Fossil energy required forPLA and for a number of petroleum-based polymers [VM 03]...

The ultimate goal of research in green composites is to replace the existing synthetic glass fibers with natural fibers as reinforcements and also to replace petroleum-based polymers with renewable-resource-based bipolymers as matrices in designing and engineering of biocomposite materials [33]. 

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